Apparatus for desalting oil



Oct. 116, 1945. H. c. EDDY 2,385,941

i APPARATUS FOR DESALTING OIL loriginal Filed Jan. 26, 1957 2sheets-sheet '2 /NL/Nrol? /35 HAROLD C. EDDY HA 9ms, K/fcH, Fos me 2HARK/s A Trae/v5 Ks.

Patented Oct. 16, 1945 APPARATUS FOR DESALTING OIL Harold C. Eddy, LosAngeles, Calif., assignor tov Petrolite Corporation, Ltd., Wilmington,Del., a l corporation of Delaware Original application January 2.6,1937, Serial No.

Divided and this application December 1, 1939, Serial No. 307,189

6 Claims.

My invention relates to av novel method and apparatus for treating oilsto remove foreign matter therefrom. Various oils can be thus puried bythe process, for example petroleum oils, topped oils, fractions obtainedby distillation per cent.

ing of other oils.

to form hydrochloric acid. Such acids arevery corrosive. Refneries facedwith this problem have found it necessary to neutralize the eiect of theacids by addition of anunonia, a procedure involving considerableexpense. In addition, salts in the incoming oil are themselves depositedon Relative to this last centrifugal processes, and, in general, any oilof relatively tube walls, thus clogging the passages, for ex- Y highresistivity capable of withstanding the ample, rendering ineffective thedesired heat potentials contemplated for production of the transfer inthe heat exchangers. Also, such salts electric field. Such oils may besubstantially appear to act as catalyzing agents tending to fuse dry, ormay contain a small proportion of water 10v coke to the heated tubes ofthe subsequent redispersed therein, the percentage of water being neiyequipmeilt- USG of the Present invention very small and never exceedingmore than a few has made possible removal 0f a majOi portion v of suchimpurities, thus increasing the life of By way of example, the inventionis well the refinery equipment, very materially increasadapted totreatment of petroleum oils or other ing the length of time that theequipment Cari be hydrocarbons preparatory to refining .or crackoperatedwithout cleaning, and resulting in the ing in subsequent refining steps.It is in this production of superior products, often with concapacity oftreating petroleum oils that the in- Sideiably increased yields. venonwill be particularly described, though factor, a 6% increase in yieldhas sometimes been the same principles can lbe applied to the treatmedein using the nVentOn- In addition. if

the invention is used in conjunction with a re- In modern renerypractice, it has been found lining system producing asphalt. the asphaltWill that the oil reaching the refinery as a refinery be of extremelyhigh Solubility, meeting Very eX- charging stock contains variousimpurities. The acting requirements often impossible to meet if watercontent thereof is usually low, seldom exthe refining equipment is usedon oil not subceeding more than a, few per cent, This water, jected totreatment in accordance with the presif present, will be in the form ofminute droplets ent inventiondispersed in the oil and various impuritiesmay Crude Oil produced by most Wells iS in the be dissolved therein, forinstance acids or various form of an emulsion, COIltanng rOm 10% t0salts, or both. Such salts may be calcium chlo- 80% water, usually inthe form of brine.v Varride, magnesium chloride, sodium chloride, etc.iouS methods have been PrOPoSed for reducing In addition, this oil maycontain various other this water content preparatory to distillation.impurities dissolved in, or dispersed in, the oil Dehydration methodsinvolving gravitational itself, as distinct from the water. Forinstance, separation, chemical treatment, this oil may contain acids orother impurities treatment, application of heat, filtration, or usepresent in the oil itself. Such acids or other imof an electric fieldhave been proposed. If all purities may simultaneously exist in the oiland of the water could thus be removed, the waterin the dispersed waterdroplets, if present. dissolved salts would likewise be taken out. How-It is an object of the present invention to reever, no dehydrationmethod has been found move impurities from oils preparatory to passagewhich will commercially accomplish such comthrough subsequent refiningequipment. these plete removal. Even with the best commercial impuritiesbeing of such character that they will dehydration methods available,the resulting oil deleteriously affect the refining equipment, as mayoften contain several hundred grams of salt by corroding the metalportions thereof or causper barrel, even if the water content has beening depositions thereon, and may deleteriously reduced to below .5%. Forinstance, subjection affect the finished product or products. of manysuch crude oils to an electricfleld will For example. the deleteriousreactions resultcause c'oalescence of the water masses and prong fromthe presence of acids in the oil are well duce an oil having a watercontent which is often knOWn- In addition. it has now been ascertainedbelow 1%. Even then, however, the salt content that certain saltsypresent in the incoming oil will of this water may be so high as toseriously afreact under high temperature t0 fOrm acids. F01' feetsubsequent rening equipment, 'Even if SuciDSanCe. Salts, such as calciumchloride or magcessive dehydrating actions are utilized on the neslumchloride. will react with water when at same oil, it will be foundimpossible to remove al1 a temperature of approximately 250 F. or above55 of the water. Many of the oils presenting the greatest problems arethose containing only a small fraction of 1% of water-oils which havebeen treated by the best lmown methods in an attempt to removesubstantially all of the water.

The present purification process can be advantageously used on suchpreviously-dehydrated oils, topped oils, or other oils of low watercontent, and will remove a major portion of the impurities, for instancethe salts, acids, or other impurities dissolved in the water, or theacids or other impurities associatedwith the oil itself. The presentpurification process should thus not be confused with the usualdehydration processes. It can well start where other crude oildehydrating processes end, and may receive a de..

dissolved impurities which are to be removed.. However, if the mixturewith its coexisting droplets is subjected to the action of an electricfield, it will be found that the droplets of the added water coalesce inlarge measure with the droplets of the original water under the actionof the electric stress. When the coalesced masses are permitted togravitationally separate, it will be found that a major portion of thewater-dissolved impurities present in the incoming oil will now beassociated with the settled water.

During this gravitational separation, the treated oil will rise. Whenanalyzed, it will usually be cent of water, and such oil may be Ian oilwhich has been previously dehydrated by any known process, or an oilnaturally containing this low percentage of water, or an oil resultingfrom mixing or blending oils of greater water content with oils of lowerwater content. In other instances. the water may be the result ofpreviously-performed steps, whetheror not they are of a dehydratingcharacter. 'I'he oils to which this invention is particularly applicableare those oils which have a very low water content, never more than afew per cent and usually less than 2%, though this water content mayoften be materially below 1/2 of 1%. The invention is also appli- .cableto theremoval of oil-associated impurities vwill thus be clear that itis not the intention of the present process to use such violent mixingas would cause the added water to become combined with the originalwater during the mixing step. The invention thus, and in other ways,departs from previous proposals, and it has been found that veryeillcient removal of impurities can be obtained by first forming amixture containing coexisting droplets of the original and added water,and then electrically coalescing these droplets, as distinct fromattempting to combine them duringthemixing step.

Best results have 'been obtained on most oils if' such mixing is used asto form a relatively loose emulsion or mixture. For instance, thisrelatively loose emulsion or mixture may desirably be of such characterthat a major portion of the added water will gravitationally separate,

partly asemulsion and partly as free water, if thev newly-formedemulsion is allowed to stand quiescent for two or three days, at theexisting elevated temperature. In some instances, the mixing can be ofsuch character that about 90% of the water will thus separate. It willbe found,

however, that this separated water will not contain any large portion ofthe salts or other waterfound to contain minute droplets of water,predominantly droplets of the added water, as distinct from droplets ofthe original water. Its salt content will be only a small fraction ofthe salt content of the incoming oil. In some instances, more than 90%of the water-dissolved impurities are removed by the process. Theprocess is fundamentally not a dehydration process. For instance, if theincoming oil contains 1% of brine dispersed in minute droplets of a sizeapproximating 1 mu, the treated oil will usually contain about the sameamount of water, sometimes slightly more and sometimes slightly less,but the water will predominantly be in the form of minute droplets ofthe added water. The particle size may still be in the neighborhood of 1mu. The net effect of the process is thus to replace in large measurethe droplets of original water in the oil with droplets of the addedwater.

The added water can usually be taken from available sources. It need notbe distilled water, and various so-called fresh Waters can be used. Theadded water may carry certain salts in low concentration, though it isessential that the added water should be relatively fresh so as not tocontain the same salts in the same concentration as present in theoriginal water droplets. Stated in other words, the added water must beof different composition from the water droplets present in the incomingoil, by which term I have reference to a difference in chemicalcomposition or a difference in concentration, or both. Differentlystated but of the same meaning, vthe added water should be substantiallymore free of the impurities to be removed than is the water forming theoriginal water droplets with which the impurities are associated. Itwill be clear that, if the added water contains the same salts as arepresent in the original water droplets, but in lower concentration, thenet salt content will be reduced by the process because of thereplacement of the original water droplets by the added water droplets.On the other hand, the chemical composition of the added water may bedifferent from that of the original water droplets, even though theconcentration is higher. In this instance, replacement of the originalwater droplets by-the added water droplets may give an oil in which thetotal salt content, expressed in grams per barrel, maybe higher thanthat of the incoming oil, but the process may still be of utility inthat the chemicals in the added water will not deleteriously affect thesubsequent process, equipment, or the products produced. Usually,howeverthe chemical composition of the added water is dierent from thatof the original water droplets, and the concentration ofthe chemicalstherein, if any, is considerably lower than the concentration of theoriginal brine droplets.

In many instances, it has been found desir- 76 able to successivelyemulsify ineen and the added water so that no single emulsifying actionneed be excessively large. It has often been found desirable toperformthe last emulsifying step immediately prior to introduction intoan electric field, for instance by using an emulsifying means fordischarging directly into the eld, though this direct introduction isnot invariably necessary, particularly on heavy oils.

From the standpoint of removing impurities dissolved in, or dispersedin, the oil, the present invention produces quite unexpected results.Assuming a substantially dry oil with acid dissolved therein, it hasbeen found possible to add water and mix to form a relatively looseemulsion. If this added water is settled out, or otherwise removedbefore subjection to an electric field, it will be found that verylittle of the acid has entered the water. However, if the mixture isformed in accordance with the present invention and is subjected to theaction of an electric field to coalesce the droplets of added Water, itwill be found that these coalesced masses contain a major portion of theacid. Just why this is the case is not completely understood, though mytests definitely show that the electric field has some action tending totransfer the oil-dissolved acids or other impurities to the Water. So,also, materials dispersed in the oil, for instance solid matter, such asmud or sand, are similarly removed, but, here again, the process doesnot cause these materials to become largely associated with the Water inthe mixing step. The action of the electric field is relied upon in thisregard,

In thus removing impurities dissolved in the oil, or molecularly `orcolloidally dispersed therein, it is not essential that the oil beSubstantially dry. Removal of such impurities is not defeated by thepresence of water droplets, though the process is best adapted to oilscontaining not more than a few per cent of water. In some instances,such dispersed Water droplets may carry certain salts, or even a portionof the acid, dissolved therein. 1n such instance, the process willreplace most of the original water droplets with droplets of the addedwater, and will also remove the impurities associated with the oilitself.

It is an object of the present invention to provide a novel method andapparatus involving the use of one or more of the above concepts in theremoval of impurities from an oil.

Various other 'objects and advantages will be evident to those skilledin the art from the following description of a selected embodiment ofthe invention. For purpose of illustration, this embodiment will bedescribed with reference to processing a petroleum oil preparatory tosub- `iection to cracking temperatures in a refining installation.

Referring to the drawings:

Fig. 1 is a pipe-line diagram of a refining system, verydiagrammatically shown, and indicates one arrangement of the inventionin conjunction therewith.

Fig. 2 is a sectional view of one type of emulsifying valve.

Fig. 3 is a vertical sectional view of the preferred form of electrictreater diagrammatically illustrated in Fig. l.

Fig. 4 is an enlarged fragmentary view of the upper and intermediateelectrode structure.

Fig. 5is a sectional vieW of the emulsifying valve discharging into theelectric field.

l Fig. 6 is a sectional view of the washing device of the invention.

In Fig. 1, I have very diagrammatically shown one type of refiningsystem I8 comprising a. fractionating means for removing variousfractions from the oil to be refined. Four refining units I2, f3, and |4are shown.

The refining unit is shown as including a still 2|, a tower 22, a heatexchanger 23, and a condenser 24. No attempt has been made to showreflux systems or speciiic details of these structures, such featuresbeing well known in the art. Suffice it to say that the incoming oil tobe refined is heated in the still 2| by any suitable heating means, thevapors moving through a pipe 25 to the tower 22. Vapors are dischargedfrom this tower through a pipe 26 which communicates with one of twopassages formed by the heat exchanger 23, these passages being inheat-transferring relationship with each other. The vapors are somewhatcooled in the heat exchanger 23, being partially condensed therein, thedischarge of this one passage communicating with a, pipe 21 whichconducts the vapors, and any condensate formed, to a pipe means in thecondenser 24. Cool water is circulated through this condenser, beingintroduced through a pipe 28 and withdrawn through a pipe 29, owingthrough a passage means which is in heat-transferring relationship withthe vapors. -These vapors are thus condensed, and the condensate isdischarged through a pipe 30.

Similarly, the refining unit I2 includes a still 3|, a tower 32, a heatexchanger 33, and a condenserl 34. The vapors move to the tower 32through a pipe 35 and to the heat exchanger 33 through a pipe 36, movingto the condenser 34 through a pipe 31. The cooling Water enters thiscondenser through a pipe 38 and is discharged through a pipe 39, thecondensate being discharged through a pipe 40.

The refining unit |3 is similarly constructed with a still 4|, a tower42, a heat exchanger 43, and a condenser 44 to which the vapors arerespectively delivered by pipes 45, 46, and 4l. The water enters thecondenser 44 through a pipe 48 and is discharged through a pipe 49, thecondensate being discharged through a pipe 50.

Relative to the refining unit I4, this unit includes a still 5|, a tower52, a heat exchanger 53, and a condenser 54, to which vapors aredelivered through pipes 55, 56, and 51. Water enters the condenser 54through a pipe 58 and is discharged through-a pipe 59, the condensatebeing discharged through a pipe 68.

These refining units are only diagrammatically shown and can beconsiderably varied in design without departing from the spirit of theinvention. Thus, in many instances, the stills and towers are combined,or various structures other than shown are utilized. However, in therefining units shown, as well as in other systems, the heat exchangerand the condenser form a heatexchange means, and it is usually desirableto preliminarily heat the incoming dehydrated oil by use of such aheat-exchange means.

In the system shown, the crude oil from the well is pumped through apipe to a suitable dehydrator 66 which separates a major part of thewater content, the water being discharged through a pipe |51.` Thisdehydrator may be of any suitable type, relying upon electricalcentrifugal, or chemical action, or upon the action of heat, or it maycomprise merely a settling means. The function of this dehydrator is toproduce a dehydrated oil having a low water content. This dehydrated oilis pumped from the dehydrator 68 through a pipe 88 by a pump 69 and isstored in a tank 10. Usually, this tank is near the retlnery, and aconsiderable length of pipe line, with or without intermediate storagemeans may be utilized to connect the dehydrator to the tank 10. It willalso be clear that any other method of forming or processing the oil tobe treated may be used. In the subsequent description of` the apparatus,it will be assumed that this oil contains about 1% of water in whichvarious impurities are dissolved, and that the oil itself contains aciddissolved therein.

This oil is pumped from the tank by a pump 1| andmoves through a pipe 12to one ofthe passages of the heat exchanger 23. Thereafter, it movesthrough a pipe 13 through the heat exchanger 33 and discharges into apipe 15 in heated condition.

In the system shown, a stream of hot water. is introduced at rightangles into the flowing stream of dehydrated oil in the pipe 15 througha pipe 16, the flow being controlled by a valve `'|1. A

preliminary mixture is formed when these liquids are brought intocontact, and this mixing action may be the first of se feral used toform the resulting, relatively loose emulsion or mixture. Thispreliminary mixture ilows through a pipe vI8 where further mixing maytake place due to turbulent iiow.

While various sources of water may be utilized, as above-mentioned, thesystem shown in Fig. 1 utilizes the cooling water ofthecondenser 34 inthis capacity. This water is heated during passage through thiscondenser and is delivered by the pipe 39 to an auxiliary heater 19where additional heat may be supplied thereto for control purposes.Various types of heaters may be utilized, 'but I have found it verysatisfactory to use exhaust steam for further heating water in theheater 19. This steam may be introduced through a pipe 80 connected to asuitable coil, the condensate being discharged through a pipe 8|. On

^ the other hand, the steam may be introduced directly into the water,if desired.

The heated water moves from the auxiliary heater 'I9 through a pipe 82to a pump 83 which develops suillcient pressure to force this hot waterthrough the pipe 16 and into` the fiowing stream of dehydrated oil inthe pipe 15.

Various means may be utilized for further mixing or emulsifying thepreliminary mixture moving through the pipe-J8. An emulsifier isindicated by the numeral 85 as receiving this preliminary mixture anddischarging samein emulsified condition into a pipe 86 leading to theelectric treater 81. Such an emulsifler may comprise any properlydesigned emulsifying device which forms an emulsion of the desiredcharacter by mechanical mixing, friction, centrifugal force, etc. OneItype of emulsifier which I have found to be very simple and effectiveis illustrated in Fig. 2 and comprises a weighted valve 88, a stem 89 ofwhich is moved downward by a linkage including an arm 90 on which isadjustably positioned a weight 9|. The position of this weight on thearm 90 controls the pressure differential on opposite sides of the valveand controls the size ofia passage 92 between a seat 93 and a valvemember 94. It thus controls the emulsifying tendency. Y.

As an auxiliary emulsiiier, I have disclosed a pump 85 capable ofwithdrawing the preliminarily-mixed -liquid from the pipe 18 through apipe 96, as controlled by a valve 91. This pump may be of any typeserving to form thedesired type of mixture, for instance, a properlydesigned and properly controlled centrifugal pump capable of forming thedesired type of mixture without in itself causing a major portion of theoriginal waterA droplets to coalesce with the added water during thepump-induced mixing action. The discharge of the pump 95 may be returnedthrough a pipe 98, as controlled by a valve 99, to the pipe 18 ahead ofthe emulsifier 85. In this instance, further mixing will take place inthe emulsifier 85. However, if this further mixing is not desired, thepump` 95 may discharge into the pipe 86 through a, pipe |00, the flowbeing controlled by a valve |0I. In some instances, the pump 95 can beutilized for emulsifying purposes exclusive of the emulsiiier 85, inwhich event a valve |02 in the pipe 86 is closed. However, in most oils,a pump-induced mixing action is not as desirable as the other mixingactions described. In other instances, the emulsier can be used to Itheexclusion of the pump by opening the valve |02 and closing the valves91, 99, and |0i. In other instances, these emulsifying means may be usedin conjunction with each other by closing a valve |03 in the pipe 18,the valves 91, 99, and |02 being open, the valve |0| being closed.

In some instances, the system will work particularly well if the mixtureflowing through the pipe 18 is divided into two streams, one ilowingthrough the emulsiiier 85 and the other flowing through the 'pipes 98and |00 to by-pass the emulsier, joining with the stream delivered fromthis emulsier at a point therebeyond. For instance, the valves 99 and|0| may be adjusted to control the amount of mixture which bypasses theemulsifler. That portion of the stream which moves through theemulsiiier will be more intimately mixed, and the by-passed stream willmix therewith when injected thereinto. The size of the added waterdroplets in the resulting mixture can thus be varied, for the dropletsin the by-passed stream may be of an average size larger than those inthe stream moving through the emulsier 85.

It is often desirable to mix the dehydrated oil and the added water insteps rather than completely mixing in a single device. This permits agradual formation of the mixture which appears to be desirable in manyinstances, as distinct from a single and more violent mixing action. Theemulsier 85 and the pump 95 may serve to successively emulsify, as canalso the pipes 18 and 86 if they are ofv small enough diameter to causeconsiderable turbulence and consequent mixing therein. In addition, ithas been found that, in some instances, better results can be obtainedby further mixing immediately prior to injection into the electriciield. For this purpose, the pipe 86 may be connected to an emulsifyingdistributor means |05 disposed in the electric treater 81 and best shownin Figs. 3 and 5.

Referring to Fig. 5, it will be noted that the pipe 86 carries a primarymember |06 which cooperates with a secondary member |01 in forming anannular discharge passage |08. Further mixing takes place as the liquidsmove through this annular discharge passage. It is often possible tomovably mount the secondary member |01, resiliently moving it toward theprimary member |06 so that the size of the annular discharge passage |08is dependent upon the quantity of the mixture moving through the pipe86. In accomplishing this result, the secondary member |01 may beprovided with a pin |08a guided in a spider |09 and carrying a spacer||0 at its lower end. A compression spring I|| is disposed be tween thespider |09 and the spacer I0 and serves to resiliently move thesecondary member |01 downward. When no liquid is moving through the pipe86, the members |06 and |01 Will be in contact, but as soon as a ow isestablished, the pressure will force the secondary member |01 upward aslight distance to open the annular discharge passage |08 in degreeproportional to the quantity of liquid to be discharged.

The details of one type of treater 81 which I have found particularlyadvantageous in the process are best shown in Fig. 3. Referring to thisfigure, this treater 81 provides a. tank ||0 including a top member ||6and a bottom member ||1, this tank being grounded as indicated by thenumeral ||8.

Suspended from insulators ||9 is a live electrode means shown asincluding an upper vlive electrode |20 and a lower live electrode |2|,rthe latter being supported from and electrically connected to the upperlive electrode |20 by rods |22.

Suspendedv from an insulator |24 and positioned between the upper andlower live electrodes |20 and |2| is an intermediate live electrodestructure |25 respectively cooperating with the electrodes |20 and 2| inproviding an upper treating space |26 and a lower treating space |21. Iprefer to form an intermediate electrode structure |25 of two electrodes|28 and |29 connected by a support |30. Y

The electrodes |20, |2|, |28, and |29 are preferably formed ofinterstitial character. A form of construction which I have foundparticularly desirable is illustrated in Figs. 3 and 4. Referring to theelectrode 20, this electrode is shown as in'- cluding inner and outerrings |32 and |33 between which extend rods or pipesl |34. Pins |36depend therefrom and carry a plurality of concentric rings |31, each ofwhich provides a lower edge |38 adjacent which the electric field isvery concentrated.

'Ihe electrode |28 is similarly formedvwith rods or pipes |40 extendingoutward from a support |4| and carrying upward-extending pins which inturn mount a plurality of concentric rings |43. The rings |43 arepreferably disaligned from the rings |31 so that the most intenseportion of any electric field established in the treating space |26 isinclined as indicated by dotted lines |44 in Fig. 4. Such anedge-to-edge field is very effective.

The electrode |29 is formed similar to the electrode |20 and providesdownward-extending rings |50. Similarly, the electrode |2| is formedsimilar to the electrode |28 and provides upward-extending rings so thata eld is establishedlin the treating space |21 similar to thatpreviously described in the treating space |26. I have found itpreferable to form the electrodes |2| and 29 of smaller diameter thanthe electrodes |20 and |28.

This type of electrode structure presents a. minimum impedance togravitational separation in the tank,||5, the rings and the supportingmeans therefor covering only a small fraction of the totalcross-sectional area of the tank. Further, the interstital nature ofthese electrodes permits free 'treating space |21.

ing directly into the treating space |21 to move the emulsion outwardtherein and successively through the edge-to-edge fields.l By properdesign of the electrical system, the potential between the intermediateelectrode structure |25 and the electrodes |20 or |2| can be made muchhigher lthan the potential between any of the live elec-A .trodes andground. -In Fig. 3, such a system is shown as including two transformers|60 and |6| connected in additive relation. `In this connection, oneterminal of each secondary winding is grounded as indicated by theknumeral |62, the high tension terminal ofthe transformer I6| beingconnected by a conductor |63 to the intermediate electrode structure|25,v and the high tension terminal of the transformer |60 is connectedby a conductor |64 -to the upper and lower live electrodes |20 and |2|Suitable switches and control means limiting the current to theprimaries of these transformers may be utilized, such means being wellknown in the art of electric dehydration of emulsions.

Assuming, for instance, that each transformer develops a potential of12,000 volts, the potential across the upper treating space |26 will be24,000 volts, as will also the potential across the lower However, thepotential between the emulsifying distributor means |05 and theelectrode |29, or the electrode I2 will be only 12.000 volts. Use ofsuch a system tends to prevent short-circuiting to the emulsifyingdistributor means |`05 and also permits introduction of the resultingmixture directly into a eld of high voltage. I believe it to be new toutilize upper and lower live electrodes with an intermediate liveelectrode in this capacity, though various other electrode systems canbe utilized without departing from the spirit of the present inventionas applied to the removal of foreign matter from oils.

The action of the electric fields is to bring into contact, and thuscoalesce in large measure, the eo-existing original and added waterparticles of the newly-formed mixture into masses of sumcient size togravitate from the oil. Thus, after the treater has been in operationfor a period, the upper end of the tank I5 will contain the treated oiland the lower end of the tank will contain a communication between theelectric ilelds and fying distributor uneans |05, the latter dischargibody of separated water. These bodies will separate at a rather definitesurface or level indicated in Fig. 3 by the numeral |10. It is desirableto rather definitely control this level to prevent grounding of theelectrode |2|. In this connection, it will be apparent that an electricfield A will be established in an auxiliary treating space |1| betweenthe lower live electrode |2| and the body of water lin the bottom of thetank ||5. If the level |10 is carried too high, this auxiliary field mayshort out. However, with proper control of the level |10, this auxiliaryfield can be utilized to further treat the settling water particles andcan be used to break an inverse-phase or reversephase emulsion, as willbe hereinafter described.

To control the water level in the tank ||5, I have shown an automaticsystem including a pipe |15 communicating w'ith the upper part of thetank ||5 anda pipe |16 communicating with a water draw-off pipe |11which opens on the lower end of the tank ||5. The pipes |15 and |16communicate with a float chamber |18 in which the oil and water are insurface contact at a level corresponding to the level |10. A properlybalanced float |19 is disposed in the chamber |18, being so formed as tooat in water and sink in oil. The position of this oat will thus changein response to changes in the level |18. This iioat'may 'be pivoted on apin |88 connected to an arm Ill which is connectedto a valve |82 in thepipe |11 by any suitable; means. such as a link |83 connected to an arm|84 ofthe valve |82 pivoted at |85 and operatively connected to the stem|88 of this valve. I! the water level rises, the valve |82 will thus beopened a further distance to drain additional quantities of water fromthe tank H and thus maintain the water level constant. Various othersystems for controlling the position of this water-level may be utilizedwithout departing from the spirit oi the present invention.,

I have found that, in some instances, there is to carry downwardtherewith particles of oil. 'I'his is not conducive to a cleanseparation, and, if allowed to continue, will result in contaminatedwater bleeds. the oil being-carried downward into a tendency for thesettling coalesced water masses v the body of water in the bottom of thetank. `If

this action takes place and is` detrimental, it can be corrected bymoving masses of water upward through' the body of water to sweep outany oil present and prevent downward movement of oil toward the waterdraw-off pipe |11.

A system which I have found very satisfactory in this regard isillustrated in Figs. 3 and 6. Disposed above and in protectingrelationship with the water draw-of! pipe |11, I illustrate a multioricedischarge head |98. This head maybe formed of a cap |92, best shown inFig. 6, and provided with a plurality of orifices |93 formed to directwater upward and outward. Certain of these orifices may be verticallydisposed,though best results are obtained if other orifices areangularly disposed relative to the horizontal. A plate |85 closes thecap |82 and receives a pipe |98 to which water is delivered by a pipe|91. The incoming water is thus sprayed into the body of water in thelower end of the tank I5 to form water masses which slowly rise towardthe surface |18 due to the inclined nature of the orices or to thermalaction, or to a difference in density if the incoming water is fresh, orto various combinations of these factors. A desirable thermal effect isobtained by`delivering to the pipe* |81 water which is slightly hotterthan the water in the bottom of the tank H5. This may be accomplished byconnecting the pipe |91 to the pipe 16, and thus to the discharge of thepump 83, the i'iow being controlled by a valve |99.

The action of these rising water masses is to sweep i'rom the body ofwater in the bottom of the tank H5 any oil or reverse-phase emulsion.

v The upward movement of the newly-added water particles moves such areverse-phase emulsion toward the surface |18 and thence into theauxiliary electric eld |1| in which such an emulsion is separated. Thisexpedient of introducing water massesk into the body of water in anelectric treater is particularlyl "aluable when treating certain oils,and permits larger quantities of water to be added to the incoming oilin the performance of the process herein-disclosed in detail. In someinstances, it is possible to accelerate the separation of the particlesoi oil in such a mass of water by adding to the water ilowing throughthe pipe |81 a. small quantity of a chemical de-emulsifying agent.Various types of such agents are known. Particularly desirable resultshave been obtained by the use of a chemical deemulsifying agent which isboth oil-soluble and water-soluble, though other chemical de-emulsltyingagents can be used.-

aaneen The treated oil moves from the upper end or the tank ||8 through;a pipe 288, the now being controlled by a valve 28| which. in turn,assists in controlling the pressure in the tank H5. This treated oilmaybe moved directly into the renning system, though I ilnd itpreferable to discharge same into a treated-oil storage tank 282 wheresome additional separation o! the water will take place. v

A pumpy 283v is shown for withdrawing the treated oil from the tank 282and moving 'same through a pipe 284 to the heat exchanger I3. Additionalheat is supplied at this point and the treated oil moves through a pipe285 to the heat exchanger 53. Being thus additionally heated, thetreated oil moves through the pipe 8| to the still 2|. Here, certainlighter fractions are removed, as previously described, the topped oilmoving'through a pipe 281 to the still 3|. This sequence is continued toremove successive fractions, and, in the embodiment shown, the heavierconstituents of the oil finally move from the still 5i through a pipe288 to a cracker 2|8. Various of such crackers are known in the art andneed not bel speciiically described. Usually. however, these 'crackersinclude a plurality of tubes which are externally heated and whichconduct the heavier constituents of the oil. The heat supplied in thecracker 2 I8 causes cracking and vaporization, the vapors moving througha pipe 2I| and being condensed in a condenser 2|2, the residue beingdischarged from the cracker-'M8 through a pipe 2|5.

By way of example, and without limiting my- 85 self thereto, operatingconditions and results with a typical oil will be given. The oil in thisexample contained only from .4% to .5% of water, but still containedfrom 100 to 250 grams of water-dissolved salts per barrel, these saltsbeing 40 predominately magnesium chloride and calcium chloride. By useof this process, it was found possible to consistently lower the saltcontent to 10 grams per barrel or less, and, in some instances, to 5grams per barrel. This oil was treated at a rate of 2250 barrels per dayper treater, and the average water content of the treated oil was, inthis instance, reduced to .2%.

In this' examplel the incoming oil moved through the heat exchangers 23and 33 and was raised to a temperature from to 150 F. The water used inthis example was withdrawn from several of the condensers 24, 34, 44,and 54, an expedient which can be utilized if desired, and was' at` atemperature of about 120 F., this temperature being increased in theheater 19 to a .value of about 160 F., a temperature which, in

this example, was somewhat above the temperature of the oil in the pipe15. The introduction of this water into the pipe 18 thus served toadditionally heat the oil, and the temperature of the preliminarymixture entering the emulsifying means was approximately F.

In this example, the available water supply was fresh water whichincidentally contained various salts in very small quantities. This wasa typical water, such as is used for drinking purposes and such as canbe obtained from lakes, rivers, domestic water supplies, etc.Percentages of water between 10% and 50% could be used with success,though approximately 20% of water gave best results in forming theresulting mixture. Operation was slightly improved by :lettingadditional water upward in the body of water in the tank H5, the waterthus introduced being at a temperatureslightly higher than that of thewater relatively stable, and substantially 90% of theI water wouldgravitationally separate from the oil as free or emulsified water il themixture was allowed to stand quiescent for two or three days at itstemperature of about 150 F. It was found that this type of emulsioncould be produced by properly controlling one or more of the emulsifyingmeans above-mentioned, but the best results were obtained when using avalve, such as shown in Fig. 2, in conjunction with the emulsifyingdistributor means I 05.

It was found desirable in this example to carry a slight pressure in theelectric treater 81. A pressure of 20 lbs/sq. in. gave very satisfactoryresults. The pressure drop across the emulsifying distributor means wasapproximately 12 lbs/sq. in., and the pressure drop across theemulsifying valve, such as shown in Fig. 2y was approximately lbs/sq.in. Additional drops in pressure due to pipe friction brought thepressure in the pipe to approximately 50 lbs/sq. in

The voltages mentioned above were used, and the water content of thetreated oil was approximately .2%. Microscopic examination of the oildischarged from the upperend of the treater 81 showed the presence ofminute water droplets of a size in the neighborhood of 1 mu,approximately the size of the original droplets present in theincomingoil. The oil withdrawn from the electric treater containedsubstantially none of the original water droplets present in theincoming oil, those water droplets present in the treated oil beingpredominantly droplets of the added water. On the other hand, the Waterdrawn from the treater was of a composite composition, containing thesalts present both in the original water droplets and in the addedwater.

Prior to installation of the invention in this exemplary refinery, itwas customary to treat this oil with large quantities of ammonia. Byproof `essing the oil as herein-disclosed before fractional distillationthereof, it was found possible to eiect a saving of approximately$300.00 per month in the amount of ammonia utilized. In addition, if therefinery equipment was utilized on oil not treated by the processherein-described, it Was found that, even if considerable quantities ofammonia were utilized, the equipment could operate for only limitedperiods without clogging. For instance, it was necessary to clean thecracker every six or ten days and the stills every fifteen or twentydays. When processing the oil by the method herein-disclosed, it wasfound that the subsequent equipment could be operated continuously forthirty-five days or more before clogging of the cracker or otherequipment took place to any detrimental extent. In addition, corrosiondiiculties were minimized and better products produced. As illustrativeof the latterfactor, this refinery was unable to produce asphalt ofthe'desired solubility prior to use of the present invention.Thereafter, the solubility of thel asphalt was raised to 99.9%.

In general, it'will be found that the process operates best if variousfactors are controlled to bring them within the following concepts. Itwill be clear, however, that the following statements are to be appliedto ranges, conditions, or values which give best results, and that thesewill vary with different oils, and that,in some instances, they do notrepresent fixed limits but can be departed from in some degree ifoptimum results are not necessary. The following suggested values applyparticularly to an oil con-` taining water in which the impurities aredissolved.

As to the added water, various waters can be used, so long as this wateris of different composition from that of the original water droplets,within the meaning of this term as hereinbeforedefined. Based on thevolume of the oil, various percentages can be used. The lower limitappears to be about 8%, and the upper limit appears to be determinedonly by the tendency to form inverse-phase emulsions in such amount asnotl to be readily treatable by the electric field. In some instances,or somewhat more can be utilized. At the higher percentages, it ispreferable to use the water spray in the bottom of the treater. Withmost oil, optimum results have been obtained between 15% and 25%,approximately 20% appearing to give the best results. The temperature ofthe water at the time it is introduced into the oil is not particularlycritical and depends, in part, upon the temperature of the oil. In someinstances, water can be introduced at room temperature, though betterresults have been obtained by use of water at elevated temperatures. Theusual temperature range is from F. to 210 F. but higher temperatures canbe used, up to the boiling point at the pressure utilized.

As to the incoming oil, various oils can be successfully treated so longas they do not shortcircuit the electrodes. The water present thereinwill be dispersed in the form of relatively small droplets, though theprocess is not limited by the exact size of these original droplets. Itis particuiarly eiective on oils in which these original waterdroplets'cannot be separated conveniently or economically. It is notalways necessary to heat the oil before injection of the added water,though heat usually improves the process. The temperature is notcritical, and excellent results have been obtained with oils from 100 F.to 225 F.

As to the resulting mixture or emulsion, the fundamental concept is todisperse droplets of the added water in the oil to coexist with theoriginal water droplets. This can be done in various ways, and if asupplementary mixing action is used, it is very desirable that themixing action should not be of such character as to itself cause a majorportion of the original droplets to combine with the added water. Themost desirable mixture is one in which a major portion of the originalwater droplets coexist with droplets ofthe added water until such timeas it is subjected to the action of the electric field. Best resultshave been obtained from a resulting mixture in which the average size ofthe added water droplets is larger than the average size of the originalwater droplets. In addition, it is often desirable to have the addedwater droplets of a heterogeneous size, though this is not alwaysessential,

In forming this type of mixture, various expedients can be used.Injection of one liquid at right angles into a flowing stream of theother, together with now through the necessary conduit communicatingwith the treater. can sometimes be used without additional mixingaction. In other instances, such a system can be used with theemulsifying distributor means ,hereinbeforedescribed. A`properly-designed pump, operated under controlled conditions can beused in some instances on certain oils withoutv additional emulsifyingmeans, or such a pump. can be used in conjunction with the mixing a tionresulting from injection, or from the use o an emulsifying distributormeans. or from bo l In other instances, an emulsifying valve, prop--`erly designed and properly icontrolled, can be used, or this can be usedin conjunction with any of the additional emulsifying means abovementioned. In some instances, particularly desirable results have beenobtained by dividing the stream of the preliminary mixture, moving aportion through a suitable emulsiiler and another portion in by-passingrelation with this emulsiier. The two streams join beyond the emulsiilerand, in so joining, an additional gentle mixing action is obtained whichrather uniformly distributes the droplets of the: by-passed streamthroughout the mixture which moves from the emulsifier.

As a general rule, the desirable type of resulting mixture or emulsionrequires a'deiinitely limited mixing action. Intimate mixing, such aswould result in homogenization, should be avoided. A centrifugal pumpmay be designed and operated to produce an emulsion departing from thedesired character and is usually not the best type of emulsifying deviceto use, except that it will work successfully on certainselected oils ifproperly designed and controlled so as not too intimately to mix the oiland the added water. If a valve, such as shown in Fig. 2. is used as theemulsifying means, the desirable pressure drop thereacross will dependupon the oil being treated and upon the other `emulsifying actions used,if any. In using such a valve with the water injection system shown andwith the emulsifying distributor means, a pressure drop thereacross from3 ibs/sq. in to 60 lbs/sq. in. has been used with success, though theselimits can often be departed from. From 5 1bs./sq. in to 15 lbs./sq. in.is usually best in this regard.

In some instances, the mixture may deslrably be heated with' or withoutheating the incoming oil or the water. Best temperatures of theresulting mixture, when subjected to the field, are from 100 F. to 199F., though atmospheric temperatures are sometimes effective.

As to the electric treater 81, any electric treater capable of bringingthe coexistng droplets together can be used, such action beinghereintermed coalescence. Alternating current fields are preferred,either constantly occurring or intermittently applied, though' suchcoalescence can take place in a uni-directional field of constant orpulsating potential. Fields resulting from the application of shortelectric surges to the electrodes, or application of peaked potentialsto the electrodes, can also be used with success. Relatively highpotentials are preferred, the potentials and type of current beingcommensurate with those used in the art of electrically dehydratingemulsions. In addition, various electrode structures can be used withvarying degrees, of success, the embodiment illustrated being foundparticularly effective.

Introduction of th'e resulting mixture or emulsion directly into theelectric neld has been found to be desirable in many instances, assludglng tendencies are almost completely eliminated by such a directintroduction. However, with heavier oils, or ,with mixtures having nodistinct sludging tendency, it is sometimes possible to intraduce theemulsion into the tank l Il at a point spaced from the main iield,allowing the emulsion to subsequently. gravitate or otherwise movethereinto. With such oils, introduction into th'e auxiliarytreatingspace lll can sometimes be.

used. While satisfactory results can sometimes be obtainedby-maintaining substantially atmospheric `pressure in the treatr 81,better results have been obtained by maintaining therein a pressure offrom 5 to 25 lbs/sq. in.

As to the treated oil moving from the upper t end of the electrictreater 81, the water content contentof the outiiowing oil is largelywithin the vand sand, are typical examples.

control of the operator. If it should be desired to even increase thetotal salt content by replacing deleterious salts with other saltshaving no detrimental action on the subsequent equipment, this can bereadily accomplished. 0n the other hand, it is possible to remove alarge portion of the salts in the original water droplets, andsubsequently re-run the treated oil through thesystem, adding saltwater, and produce a salty oil, thus indicating that the replacementaction mentioned above is reversible.

Temporary storage of the treated oil in tank 202 is not essential,though it will be found that some additional separation of water willtake place therein, and this expedient is often desirable in refinerypractice.

Coming now to the general problem of removing impurities associated withthe oil, as distinct from being associated with any water droplets whichmay be present, such impurities may be dissolved in, or dispersed in,the oil. Various acids dissolved Ain the oil and various impuritiescolloidally dispersed in the oil. for instance mud Assuming that theincoming oil contains not more than a vfew percent of water. and thatthis water carries various impurities which will be removed as above seeforth, it will be clear that acids thus dissolved in the water dropletswill be removed along with other impurities, such as salts, etc.Assuming that this incoming oil also contains acid dissolved `in the oiland mud colloidally dispersed therein,

it has been` found that the process will remove substantial amounts ofthese impuritiesby following the procedure outlined above. Just why thisis the case is not distinctly understood. It

` from the ou to the water, and

" sulting mixture is readily water present therein.

2,886,941 y with the als or medecine. nem into ou separated intheelectric treater.

v So, also, the invention vis applicable to removal cfimpurities-dissolved in, or dispersed in, the oil, regardless of whetheror not water dropletsl are present. For instance,it has beenIoundfpossible to remove oil-dissolved acid and colloidally-dispersedimpurities from an oil which is substantially dry. In this instance,water is added in about the same proportions as mentioned above. One ormore mixing steps, as above-defined, can be utilized, though, ingeneral, it can be stated that a somewhat more violent mixing action canbe utilized in this connection so long as the retreatable by anelecdroplets of the added Here again, it has been found that th'eoil-dissolved acid and the colloidally-dispersed impurities becomeassociated with the added water by some action in the electric eld, andnot in lthe mixing step itself. Acids. or other impurities dissolved in,or dispersed in, an oil can thus be removed by the process.

The invention is not limited to treatment of an oil preparatory toadditional rening by fractional methods. Various other uses of theinvention will be apparent to those skilled in the art. If used with areiinery system, the connections disclosed will be found of particularutility in savlng heat, utilizing the water from the condenser means,and being desirable in other connections. However, the invention isapplicable to various types of refining units, and need not be connectedthereto in heat-transferring relationship if this tric eld to coalescethe is not desired.

While the process has been particularly defined with reference to adehydrated oil, it is applicable to removing impurities from variousoils under the principles outlined above, regardless of whether theyhave been previously treated in one way or another, and regardless ofwhether they are to be additionally treated by fractionation. Nor is italways essential that the oil be of lower gravity than the added water.If the converse is true, the principles herein-disclosed can be appliedby withdrawing water from the upper end of the treater tank, and thehydrocarbon from the lower endI suitable changes in position of theinsulators being made to prevent short-circuiting of the electrodes.Such conditions may be met in treating certain tars to remove impuritiestherefrom.

The term "relatively fresh water, as used in the claims, has reference,if the oil carries dispersed impurity-containing water, to a `waterwhich, ii.' it contains any of the impurities to `be removed. has amaterially less concentration thereof than does the dispersed water, or,if the oil carries no dispersed impurity-containing water, the term hasreference to a water which has no more'than a small concentration of theimpurities to be removed.

In general, the present process vcomprises .the treatment of a mineraloil containing no more than a few-per `cent of waterl by mixing arelatively freshwater therewith preparatory to electric treatment. `Thecharacter of mixing -is important and, as previously pointed out, mustbe limited to a value at which the desiredaction will be obtained.Thismixing shouldv be of such character as to disperse the relativelyfresh water eiIectively throughout. the oil and-to form an emulsionwhich is in a condition'to be continuously and substantially Ycompletely resolvable appearin the water at the junction of which saidstreams of oil and l and water, without the accumulation of such amountof sludge comprising" unresolvedemulslon as would interferefwithfthemaintenance ol.' the electric field. Any such-increasing accumulation ofsludge would seriously interfere with thek continuity of the process,iwhich, being often connectedto refinery equipment,` must remainon-stream for long periods of time. In addition, electric treatment well`suited to` the articial emulsion `or mixtureashould be. used, andshould tained by subjection to an electric field and separation of thecoalesced water masses.

Various other changes and modiflcations can be made without departingfrom the spirit of the present invention as deiined in the appendedclaims. y

This application is a division ot myco-pending application, Serial No.122,470,- led January 26, 1937 (now Patent No. 2,182,145), which is acontinuation-impart of my abandoned application, Serial No. 66,404,illed February 29, 1936.

I claim as my invention:

1. Apparatus for purifying salty mineral oils of low water content,including in combination: a tank closed from the atmosphere; electrodemeans in said tank for establishing a coalescing electric field therein;means for continuously forming an electrically-treatable oil-continuousdispersion, said means including a pipe means providing astream-contacting zone, means for continuously delivering tosaid'stream-contacting zone lof said pipe means under superatmosphericpressure proportioned streams of the salty oil of low water content tobe purined and relatively fresh water to preliminarily mix said saltyoil and-said relatively fresh water in said zone said streams, and adistributor means at the end tributor means stant of discharge from saidpipe means into said tank to produce said oil-continuous dispersion,said distributor discharging saiddispersion into said tank in a positionto be treated by said coalescing electric eld to coalescer the dispersedwater into masses containing saltsremoved from the oil and saidpreliminary mixture -beingadditionally mixed beyond saidstream-contacting zone solely by passage of said distributor meansat thepoint of discharge into .said tank except for incidental mixing causedby ow of said lpreliminary mixture along said pipe means to saiddistributor means, said superatmospheric pressure `under water arebrought together in said zone being sufdcient to advance saidpreliminary mixture along said pipe means and through saidldistributormeans 1 and 'being sufcient to maintain a superatmosphericpressure in said Vtank to avoid any necessity of pumping saidpreliminary mixture Vafter formation thereof which pumping of suchpreliminary mixture would make the oil-continuous dispersion lesssusceptible to electric treatmentsa id tank be capable of continuouslytreating same so that substantially complete resolution cana' beobpassage through lsaid restrictedv at which said streams of water andoil are brought together. I

2. A combination as defined in claim l. in

which said distributor means includes two members forming saidrestrictedA e, means for wtrol the 4intensity of said additional mixingaction of said distributor means on said prelimmary mixture at theinstant of discharge from saidpipemeansintosaidtank. A

3. Apparatus for purifyingA mineral oil of low water content, whichcomprises: separating means for coalescing and separating the aqueousphase of a water-in-oil type emulsion, said separating means including atank closed from the atmosphere and containing electrodes forestablishing a coalescing electric neld in said tank; a pump for anaqueous medium; a pump for said oil, each of said pumps having anoutlet: pipe means connected to the outlets of'said pumps, said pipemeans having a -juncture for commingling streams of said oil and aqueousmedium from said pumps to form a combined stream and providing `aconduit for said combined stream; a mixingmeans having a ,restrictedpassageway therein and connected to said conduit for mixing saidcombined stream; discharge -means for discharging the mixed stream intothe interior of said tank for treatment in said eld; a conduitconnecting said mixing means to said discharge means, said restrictedpassageway of said mixing means being substantially smaller incross-sectional area than the interior of either of said conduits, saidpumps forcing said com- -bined stream to iiow through said mixingmeans,said conduits, and to said discharge means with progressive pressurereduction during such now, the mixing of thel oil and aqueous medium ofsaid combined stream forming said emulsion and being eiiectedexclusively lby agitation induced by such ilow and lthis flow beingeffected exclusively by' said pumps; and means for separatelywithdrawing aqueous medium containing impurities from said'oil andpurified oil from said separating means.

4. Apparatus forvpurifying mineral oil of low water content, whichcomprises: separating means for coalescing and separating the aqueousphase of a water-in-oil type emulsion, said separating means including atank closed from the atmosphere and containing electrodes forestablishing a coalescing electric field in said tank; pipe means for anaqueous medium; pressure means for forcing said aqueous medium throughsaid pipe means; pipe means for said oil; pressure means for forcingsaid oil through said lastnamed pipe means, said pipe means forsaidaqueous medium and said oil having a juncture for commingling streams ofsaid oil and aqueous medium from said pressure means to form a combinedstreamY and providing a conduit for said combined stream; a mixing meanshaving a restricted -passageway therein and connected to said conduitfor mixing said combined stream: discharge means for discharging the-mixed stream into the interior of said tank for treatment in saidfield; a 'conduit connecting said mixing means to said discharge means,said restricted passageway of said mixing means being waterl content,which comprises:

substantially smaller in cross-sectional area than the interior ofveither of said conduits, said pressure means forcing said combinedstream to iiow through said mixing means, said conduits. and to saiddischarge means with progressive pressure reduction during such now, themixing of the oil and aqueous medium of said combined stream formingsaid emulsion and being eifected exclusively by agitation induced bysuch i'lowvand this flow being effected exclusively by said pressuremeans; and means for separately withdrawing aqueous medium containingimpurities from said oil and purified oil from said separating means.

5. Apparatus for purifying mineral oil of low separating means forcoalescing and separating the aqueous phase of a water-in-oil typeemulsion, said separating means including a tank closed from theatmosphere and containing electrodes for establishing a. coalescingelectric field in said tank; pipe means for an aqueous medium; pressuremeans for forcing said aqueous medium through said pipe means; pipemeans for said oil; pressure means for forcing said oil through saidlastnamed pipe means. said pipe means for said aqueous medium and saidoil havinga juncture for commingling streams of said oil and aqueousmedium from said pressure means to form a combined stream and providinga conduit for said combined stream; a first mixing means having arestricted passageway therein and connected to said conduit for mixingsaid combined stream: discharge means for discharging the mixed streaminto the interior of said tank for treatment in said eld and comprisinga second mixing means having a restricted passageway; a conduitconnecting said rst mixing means to said discharge means, saidrestricted passageways of said rst mixing means and said discharge meansbeing substantially smaller in cross-sectional area than the interior ofeither of said conduits, said pressure means forcing said combinedstream to iiow through said rst mixing means. said conduits, and saiddischarge means with progressive stream forming said emulsion and beingeffected exclusively by agitation induced by such ow andthia iiow beingeffected exclusively by said pressure means; and lmeans for separatelywithdrawing aqueous medium containingimpurities from said oil and puriedoil from said separating means.

6. Apparatus for purifying mineral oil of low water content, whichcomprises: means for coalescing and separating the aqueous Y phase of awater-in-oil type emulsion. said separating means including a tankclosed from the atmosphere and containing electrodes for establishing acoalescing electric iield in said tank; pipe means for an aqueousmedium; pressure means for forcing said aqueous medium through said pipemeans; pipe means for said oil; pressure means for forcing said oilthrough said lastnamed pipemeans, said pipe means for said aqueousmedium and said oil having a juncture for commingling streams of saidoil and aqueous meseparating conduit means having at least onerestricted passageway positioned therein and forming a mixing means formixing said combined stream to form said mixed stream, said restrictedpassageway being substantially smaller in cross-sectional area than theremainder of said conduit means, said= pressure means forcing saidcombined stream to ow through said conduit means including said mixingmeans with progressive pressure reduction

